Systems and methods for measuring and characterizing interior surfaces of luminal structures

ABSTRACT

A digital topographic model of the luminal surface is generated by projecting an optical pattern on the luminal surface from the first location within the lumen. At least a portion of the projected pattern is detected from a second location within the lumen which is based apart from the first location. The dimensions of the luminal wall can be measured by triangulation in order to produce the digital topographic model of the body lumen.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/263,698 (Attorney Docket No. 41784-703.201), filed Apr. 28, 2014,which claims the benefit of U.S. Provisional Application No. 61/818,849(Attorney Docket No. 41784-703.101), filed May 2, 2013, the entirecontent of which is incorporated herein by reference.

BACKGROUND OF THE INVENTIONS 1. Field of the Invention

The present invention relates generally to medical devices and methods.More particularly, the present invention relates to systems and methodsfor optically scanning an interior surface of a body lumen to generatedigital dimensional information relating to a lumen surface.

Minimally invasive implantation of vascular and other luminal prostheseshas become widespread in the last ten years. The intravascular deliveryand implantation of stent grafts for treating abdominal and otheraneurysms is now common place for patients at risk for receiving opensurgical implantation procedures. The percutaneous delivery andimplantation of prosthetic aortic valves has recently become availableand is quickly becoming a preferred treatment option for patients atrisk for receiving open heart surgery. Both of these procedures, andother percutaneous therapeutic procedures, would benefit fromcharacterization of the site of implantation prior to choosing theimplant and performing the implantation procedure. Presently, externalimaging, such as CT and Mill, is the most common technique for obtaininganatomical information regarding the implantation site. CT and MRI,however, provide limited dimensional information. The images which areobtained must be interpreted in order to derive dimensional informationwhich is often inaccurate.

Intravascular ultrasound imaging (IVUS) can also be used to characterizeaneurismal and valve replacement sites prior to implantation procedures.The IVUS probes are intravascularly placed within the blood vessel orheart. While the ultrasonic images may be improvements over thoseobtained by external scans, the images still lack the dimensional detailwhich would be desirable for selecting a prosthesis for subsequentimplantation. These images also suffer from artifacts which make itdifficult to interpret the anatomical boundaries of the structures,further leading to inaccuracy in determining dimensions.

A further shortcoming of both the external and internal imagingmodalities is an inability to measure the luminal area and anatomicaldimensions when the body lumen is under deformational stress equivalentto that provided by the prosthetic implant. For example, when planningthe implantation of a prosthetic heart value, it would be useful todetermine the dimensions of the valve annulus and surrounding tissueswhile the annulus was placed under a radially expansive force equivalentto that provided by the prosthetic implant. The conventionally utilizedimaging methodologies do not allow measurement of the annulus diameterwhich would be assumed after a prosthetic device is deployed.

For these reasons, it would be desirable to provide improved methods,devices, and systems for obtaining dimensional information regarding animplantation site in a body lumen prior to actual implantation of aprosthesis. It would be particularly desirable if the dimensionalinformation could be measured directly, not indirectly through imageinterpretation, and if the measurements could be made while the luminalsite is under a stress or other deformational force which is analogousor equivalent to that which would be provided by the implant afterimplantation. It would be further desirable if the methods, devices andsystems used for obtaining the measurement information could also obtainother information, such as color or other characteristics of the tissuebeing scanned during measurement. At least some of these objectives willbe met by the inventions described below.

2. Description of the Background Art

Balloons and other devices for sizing valve annuluses and other lumensare described in U.S. Pat. Nos. 6,110,200; 6,755,861; and 8,246,628 andin U.S. Patent Publ. Nos. US2012/289982; US2012/065729; US2011/276127;US2011/237940; US2011/098602; US2010/198346; US2010/168839;US2007/244552; and US2005/075724.

SUMMARY OF THE INVENTION

The present invention provides methods, devices and systems for directlymeasuring dimensions and other characteristics of a luminal structure ina patient body. As used hereinafter and in the claims, the phrase“luminal structure” refers to all body lumens, passages, open bodycavities, closed body cavities and the like, specifically includingheart valve annuluses, aneurysms, left atrial appendages, and vascularlumens (particularly including occluded regions of the vasculature),including prosthetic implants implanted in such structures, such asstents, stent grafts, heart valves and the like. In particular, thepresent invention provides for direct measurement of a lateral or radialdimension(s) of a body lumen over a discrete axial length of the lumen.Dimensions will be acquired using optical tools and will be typically becalculated based on the relative positions of an illumination sourcewithin the body lumen and a light sensor also in the body lumen butspaced-apart from the illumination source. The illumination sourceprojects a pattern of light over a region of the lumen wall to bemeasured, and the lateral or radial dimensions can be calculated usingtriangulation. The dimension may be determined in a variety of ways, butwill usually be acquired as points or lines in a three-dimensional spaceusing conventional radial or Cartesian coordinate systems. Thedimensional information is usually provided in digital files, and thedigital files can be represented as wire frame, solid or otherconventional images on a display screen. The resulting dimensionallyaccurate images may then be overlaid with dimensionally accurate imagesof a prosthetic device intended to be implanted. The physician or theuser can then visually determine the adequacy of the intended implant.Alternatively or additionally, checking algorithms can be used to assessfit of the prosthesis. Such dimensional information, however, is usefulin many other circumstances, such as in the sizing and design of customimplants which can be made to precisely match the anatomical dimensionsof the target body lumen or other anatomical space.

The present invention will typically utilize optical probes and toolsfor the direct measurement and characterization of an inner wall orother interior structure of the body lumen. Usually, an optical patternis projected on the wall where the pattern may be stationary or scannedover the wall. The pattern may be projected directly onto a luminalwall, but will more usually be projected onto or through an inner wallof a balloon or other conformable structure which has been deployedwithin the target body lumen. The balloon may be elastic so that itinflates and conforms to the interior surface of the luminal wall.Alternative, the balloon may be inelastic but oversized so that it willconform to the luminal wall with folding where excess balloon materialexists.

The probes and tools of the present invention will typically include atleast one illumination source and at least one light sensor to capturethe light from the illumination source after it has been reflected fromthe luminal wall or interior of a balloon. A complete pattern may beprojected from the illumination source to cover all or a major portionof the luminal wall with a known geometry so that the light sensor candetermine the elevation angles of different points, lines or othercomponents of the pattern, allowing the radial dimension of the wall atany particular point on the pattern to be calculated by triangulation.More usually, however, point, line, ring or other discrete opticalpattern will be projected from the illumination source, and light fromthe illumination source will be physically or electronically scannedover the interior surface of the body lumen or balloon. The probe ortool, typically in the form of a catheter, will be connected to deliveranalog or digital data to a computer or other processor which in turncan generate three-dimensional models of the luminal wall geometry ofthe body lumen. Typically, the processor may utilize finite elementmodeling (FEM) techniques in calculating the three-dimensional modelswhen considering the change in geometry due to deformational forces.

The catheters utilized in the present invention may have generallyconventional structures as needed to reach their target anatomy. Forexample, the bodies of the catheters intended to measure the dimensionsof an aortic valve annulus will be structured to be introduced to theannulus, typically by the same route as intended for the subsequentimplementation. Thus, the catheters can be structured to be introducedinto the femoral artery and over the aortic arch. Alternatively, thecatheters may be structured to be advanced transapically into the heartand aortic valve annulus. Catheters intended for imaging an abdominalaortic aneurysm (AAA) will typically be configured to be introduced intoa femoral artery and upward into the abdominal aorta. Catheters may alsobe configured for introduction through laparoscopic, thoracoscopic, orother known techniques for introducing catheters and probes into thebody.

The catheters of the present invention may be configured for directscanning and measurement of the body luminal where the illuminationsource and light sensor are mounted at or near a distal portion of thecatheter in such a way that they may be directly exposed within the bodylumen. More typically, however, the catheters will include an inflatablestructure, e.g. a balloon, configured to cover the illumination sourceand light sensor during use. In particular, when the catheters areintended to be used in a vascular environment, where blood can obscureoptical measurements, it will be useful to provide an opticallytransparent environment surrounding the illumination source and thelight sensor so that the pattern may be projected and detected withoutinterference. By inflating a balloon with such an optically transparentmedium, the optically transparent environment can be easily obtained. Byoptically transparent, it is meant that the medium will allow light of apreselected wave length (or wave lengths) to be transmitted, reflectedand detected within the luminal environment without substantialinterference or attenuation.

Alternatively, at least a distal portion of a catheter body could beformed from an optically transparent material that allows the passage oflight through the catheter body wall as defined above. The illuminationsource and light sensor can then be placed in an interior passage orlumen within the transparent distal portion of the catheter body to scanthe luminal wall. As the catheter body will usually not be expandable,in some instances in may be desirable or necessary to clear the opticalfield surrounding the transparent section of the catheter body with afluid that allows the passage of light as will be described in greaterdetail below.

When using a balloon, the balloon will typically be inflated to conformto the interior surface of the luminal structure. The balloon can behighly compliant and “elastically” conform to the structure.Alternatively, the balloon can be inelastic or non-compliant but have alarger width or transverse dimension than the body lumen to be measured.Excess balloon material will simply fold over or be compacted after theballoon is fully inflated. In either case, the balloon inflationpressure may be set relatively low so that the balloon will conform tothe interior of the luminal structure with little or no deformation ofthe lumen. Alternatively, the balloon can be inflated to higherpressures which cause deformation (expansion) of the luminal wall. Suchhigher pressure inflation can allow estimation of the luminal walldimensions after implantation of a particular device, such as a stent,valve, or other device which will apply a radially outward force againstthe luminal wall. By inflating the balloon to a pressure which isgenerally equivalent to the expected expansive force of the implantedprosthesis, the dimensions of the lumen after deployment of theprosthesis can be accurately predicted.

The balloons utilized in the catheters of the present invention may betransparent, in which case all or at least a portion of the light fromthe illumination source will reflect from the inner wall of the bodylumen. Alternatively, the balloon can be opaque and/or have a moderatelyor highly reflective inner surface. In the latter cases, at least aportion of light from the illumination source will reflect from theinterior of the balloon wall.

Once the catheter or other probe has been deployed and the balloon hasoptionally been inflated, the illumination source is energized toproject a pattern on the interior surface of either the luminal wall orthe balloon. The light sensor(s) detect the projected optical patternincluding the apparent angle or elevation of points, lines or theportions of the optical pattern relative to the light sensor. Using theknown position and geometry of the projected optical pattern and theangle or elevation of the observed reflected light, the dimensions ofthe optical pattern can be calculated. As the optical pattern is presentat or near the interior wall of the body lumen, the calculateddimensions in geometry are equivalent to the dimensions of the bodywalls at the time the measurements are made.

When the projected light is reflected directly from a luminal wall orthrough a transparent balloon, the color and/or florescent content ofthe reflected or emitted light can be analyzed to yield informationregarding the tissue composition. For example, if white light isprojected and red light is received, it will be apparent that the tissueis red. Similarly, reflected yellow light or white light will tell thephysician that the luminal wall is yellow or white, respectively. Inother instances, non-white light can be used as the illumination sourcein order to determine other characteristics of the tissue, such astissue fluorescence, and the like. Such color information can be useful,for example, in detecting the presence of vulnerable plaque in thevasculature.

In a first aspect of the present invention, a method for generating adigital topographic model of a luminal surface of the body lumencomprises projecting an optical pattern on the luminal surface from afirst location within the body lumen. At least a portion of the lightreflected from the projected pattern is detected from a second locationwithin the lumen where the second location is spaced-apart from thefirst location. The digital topographic model is then generated bytriangulating the detected pattern from the projection and detectionlocations. For example, triangulation can be based on determiningprojection and detection angles and calculating the radius of the lumenbased on the distance between the first and second locations.

In specific embodiments, projecting comprises projecting light from atleast one illumination source located within the lumen. Optionally, theillumination source may be translated along a path through the lumen inorder to scan the projected pattern over the luminal wall. Thetranslation path will extend over a “characterization” distance orlength of interest within the body lumen, typically in a range from 5 mmto 250 mm, usually from 10 mm to 150 mm, with specific distances setforth below for different body lumens. The specific length of thetranslation path will depend heavily on what luminal structure is beingmeasured and for what purpose. An aortic valve annulus would usuallyrequire a different characterization length than would an aorticabdominal aneurysm (AAA), a left atrial appendage, a region of thevasculature, or the like. Specific exemplary characterization lengthsare set forth in Table 1 below for different anatomies. The projectedpattern may have a variety of geometries but will often be a circular orring pattern which circumscribes a cross-section of the lumen. Byadvancing such a ring or circle pattern axially through the lumen, thecross-sectional dimensions of the body lumen can be calculated over thescanned length.

TABLE 1 Exemplary Characterization Lengths Characterization LengthDiameter of Lumen Anatomical Site Max/Min Min/Max Aortic valve Complex30 mm-50 mm 20 mm-40 mm Illiac arteries 160 mm-250 mm  5 mm-20 mmAbdominal aortic Aneurysm  10 mm-250 mm 10 mm-30 mm Left Atrialappendage 20 mm-50 mm  5 mm-15 mm Vasculature  5 mm-150 mm  3 mm-20 mm

Typically, detecting at least a portion of the projected pattern willcomprise sensing light from the illumination source reflected from theluminal wall and/or balloon interior with at least one light sensorposition within the lumen. The light from the illumination source willhave been reflected from the wall so that the sensor will observe theapparent position of the projected light on the wall when it is struckby the light. The sensor may be a CCD, CMOS, or other array detectorwhich can determine the location of pixels which detect the light. Usingsuch technologies, the angles of incidence of light across the sensorand associated lenses may be calculated.

In specific embodiments, the light sensor may be coupled to theillumination source so that they may be translated in tandem through thelumen. By coupling the light sensor at a fixed distance to anillumination source that projects a ring of light radially outward,preferably at a perpendicular angle relative to an axis of travel,triangulation can be readily achieved based on the detected angle of thelight sensed by the light sensor.

In another specific embodiment, at least one light sensor may remainstationary while the illumination source is translated through thelumen. The illumination source will typically project a ring patternradially outwardly at an angle perpendicular to the axis of travel. Thefixed light sensor can track the angle of incidence of the reflectedlight as the distance between the sensor and the illumination sourcechanges and is tracked.

In still another specific embodiment, the illumination source includes aplurality of individual illumination sources which are distributed alonga path through lumen. Usually, but not necessarily, the distributedillumination sources will be fixed and will not move relative to eachother or to the light detector(s). Alternatively, it would be possibleto move some or all of the plurality of illumination sources althoughthat would generally not be preferred. The plurality of illuminationsources will typically extend over a characterization distance in therange from 5 mm to 250 mm, usually from 10 mm to 150 mm, with specificranges for different anatomies being set forth in Table 1 above. Theillumination sources will typically project a ring pattern whichcircumscribes a cross-section of the lumen surrounding the source in amanner similar to the axially translating illumination sources. In otherinstances, at least some of the plurality of illumination sources mayproject patterns which are geometrically different from one or morepatterns projected by others of the illumination sources. Additionally,in some instances, at least some of the plurality of illuminationsources will project a pattern having a different light wavelength thanthose projected by one or more of the other illumination sources.

In still further aspects of the methods of the present invention, anillumination source and a light detector may be coupled together,usually at a fixed distance, and the resulting assembly drawn through abody lumen, optionally over a guidewire or other guiding element. Theillumination source will typically project a circumferential ring, andthe light detector will measure the reflection angles which in turn canbe used to triangulate the radial distance to the luminal wall surface(based on the known usually fixed distance between the illuminationsource and the light detector) circumferentially at all points over thelength through which the catheter is drawn.

Detecting the reflected light will typically comprise sensing light fromthe at least one illumination source, where the light from theillumination source is first reflected from the wall and/or an innerballoon surface within the lumen. In some embodiments, a single lightsensor may be utilized where the single light sensor may be located atone end of one or more illumination sources. In other instances, two ormore light sensors may be utilized where at least one light sensor willbe at one end of the illumination source(s) and a second illuminationsource will be at another end of the plurality of illumination sources.The use of addition light sensors will increase the field of view of thelight sensors thus allowing increased coverage of the luminal walland/or increased accuracy.

As used herein and in the claims, the phrase “luminal surface” willinclude both a fully exposed luminal surface free from coveringstructures as well as a luminal surface which is covered by a balloonstructure or other membrane. Usually, such balloon structures or othermembranes will conform to the luminal walls so that the contours andgeometries of the luminal wall will be imparted to the balloon or lumensurface. Frequently, the methods of the present invention will compriseinflating a balloon within a body lumen so that the balloon conforms tothe luminal surface. As described above, the balloon may be elastic orinelastic, and the light from the illumination source may be reflectedfrom the inner wall of the balloon. Alternatively, when the balloon istransparent to at least a portion of the illumination wavelength, theillumination light may penetrate through the balloon and be reflecteddirectly from the luminal wall. When the balloon is not transparent, itwill usually have an inner surface with enhanced reflectivity, forexample being coated with a material which enhances specular reflection.

Methods of the present invention are suitable for generating digitaltopographic models of virtually any human or animal body lumen but willbe particularly useful for modeling heart valve annuluses, aneurysms,vascular occlusions, and the like. In particular, the methods are usefulfor determining the topographic models of aortic valve annuluses priorto prosthetic valve implantation and for determining the topographicmodels of abdominal aortic aneurysms prior to implantation of stentgrafts or other procedures.

While the methods of the present invention are particularly useful forthe determination of topographic models, the methods are also useful foranalyzing the nature of the luminal wall being scanned. For example, thewavelength or other optical properties of the light and/or fluorescencereflected or emitted from the luminal wall may be analyzed in the orderto determine some wall characteristic, such as the nature of occlusiveor diseased materials in a blood vessel. In specific incidences, theprojected light may comprise two or more different wavelengths allowingsimultaneous analysis of different properties specific to each of thewavelengths.

In a second aspect, the present invention provides catheters and devicesfor scanning a luminal surface of a body lumen to generate electronicsignals useful for providing a digital topographic model of the luminalsurface. Such catheters comprise a catheter shaft having a distal endand a proximal end. At least one illumination source is mounted at ornear a distal portion of the catheter shaft. The illumination source istypically configured to project an optical pattern onto the luminal wallwhen the distal portion of the catheter is in the body lumen. At leastone sensor is mounted on or near the distal portion of the catheter at alocation spaced-apart from the location of the illumination source. Thissensor is configured to sense light from the illumination source whichhas been reflected from the luminal wall and to produce an electronicsignal representative of the reflected light pattern. The digitaltopographic model can be generated by triangulation based upon theprojected optical pattern, a distance between the illumination sourceand the sensor, and the electronic signal, where the electronic signaltypically includes information representing the angles and elevations ofboth the light projected from the illumination source and the lightdetected by the light sensor.

In a first embodiment, the at least one illumination source is mountedto axially translate over the distal portion of the catheter shaft.Typically, the at least one illumination source will be able totranslate over a distance in the range from 5 mm to 250 mm, usually from10 mm to 150 mm, with specific ranges for different anatomies being setforth in Table 1 above. The illumination source may project a widevariety of specific patterns, with a ring pattern often being employed.

The at least one light sensor will typically be coupled to theillumination source so that the light sensor is able to translate intandem with the illumination source. Such coupling will provide a fixeddistance between the illumination source and light sensor in order tosimplify the triangulation calculations.

In other specific embodiments, the at least one light sensor may befixedly mounted on the distal portion of the shaft, usually being on aproximal or distal side of the at least one illumination source. Often,at least a second light sensor will also be fixedly mounted on theshaft, most often on the other side of the at least one illuminationsource. In this way, the at least one illumination source may translatebetween the two fixed light sensors in order to provide for improvedtracking of the projected light pattern.

In still other embodiments, a plurality of illumination sources may bedistributed over the distal portion of the shaft. The plurality ofillumination sources may be distributed over a distance in distance inthe range from 5 mm to 250 mm, usually from 10 mm to 150 mm, withspecific ranges for different anatomies being set forth in Table 1above. Typically, at least some of the plurality of illumination sourceswill project a ring pattern which circumscribes a cross-section of thelumen surrounding the source, although a variety of other illuminationsources would also be available. The plurality of illumination sourcesmay all project the same pattern or at least certain ones of theillumination sources may project patterns which are different thanothers of the illumination sources. Similarly, the plurality ofillumination sources may project light of the same wavelength orindividual ones of the light illumination sources may project lighthaving different wavelengths than that projected by others of theillumination sources.

Usually, although not necessarily, an inflatable balloon will be securedto the shaft over the illumination source and the light sensor in orderto isolate the illumination source in the light's sensor from theluminal environment. The balloon may be elastic or inelastic, but willin at least most cases conform to the luminal wall when inflated withinthe body lumen. The balloon may have a reflective interior surface ormay be fully or partially transparent in order to allow light from theillumination source to penetrate the balloon and reach the luminal wall.

The catheters of the present invention may be incorporated into systemscomprising the catheter in combination with a processor connected toreceive the electronic signal from the catheter. The processor willtypically be configured to generate the digital topographic model bytriangulation based upon the projected optical pattern and the distancebetween the illumination source and the sensor. The processor may alsobe able to analyze color and other characteristics of the reflectedlight detected by the light sensor, where the light or othercharacteristics may be diagnostic of luminal conditions, such as thenature of plaque within a diseased blood vessel.

INCORPORATION BY REFERENCE

All publications, patents, and patent applications mentioned in thisspecification are herein incorporated by reference to the same extent asif each individual publication, patent, or patent application wasspecifically and individually indicated to be incorporated by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features of the invention are set forth with particularity inthe appended claims. A better understanding of the features andadvantages of the present invention will be obtained by reference to thefollowing detailed description that sets forth illustrative embodiments,in which the principles of the invention are utilized, and theaccompanying drawings of which:

FIGS. 1A-1C illustrate a first embodiment of a catheter constructed inaccordance with the principles of the present invention where anillumination source and a light sensor are mounted to axially translatein tandem within a conformable balloon.

FIG. 1D illustrates a modified first embodiment of a catheterconstructed in accordance with the principles of the present inventionwhere an illumination source and a light sensor are mounted to axiallytranslate in tandem within a transparent cylindrical extension of thecatheter shaft.

FIGS. 2 and 2A illustrates a second embodiment of a catheter constructedin accordance with the principles of the present invention, where anillumination source is mounted to axially translate within a balloon anda single light sensor is fixed to a shaft of the catheter on one side ofthe translatable illumination source. FIG. 2 shows the catheter in aluminal environment without a stent and FIG. 2A shows the catheter in aluminal environment with a stent.

FIG. 3 illustrates a third embodiment of a catheter constructed inaccordance with the principles of the present invention, wherein anillumination source is mounted to axially translate between a pair oflight sensors within a balloon.

FIG. 4 illustrates a fourth embodiment of a catheter constructed inaccordance with the principles of the present invention, where aplurality of fixed illumination sources are mounted between a pair offixed light sensors within a balloon.

FIGS. 5A and 5B illustrate a fifth embodiment of a catheter constructedin accordance with the principles of the present invention, where anillumination source comprises a plurality of partially reflectivemirrors disposed along a light conduit with a single light sensor at oneend of the illumination sources with no balloon.

FIGS. 6A and 6B illustrate a sixth embodiment of a catheter constructedin accordance with the principles of the present invention with two ormore illumination sources configured to axially translate on a distalportion of the catheter with two or more aligned light sensors, whereinthe distal end of the catheter is configured to permit perfusion and theillumination sources and light sensors are within a balloon.

FIGS. 7A-7C illustrate a seventh embodiment of a catheter constructed inaccordance with the principles of the present invention, where a singleillumination source and single light sensor are fixedly mounted at thedistal end of a catheter within a balloon, where the catheter isintended to be drawn through a body lumen in order to scan the luminalsurface.

FIG. 8 is a schematic representation of systems of the present inventionincluding the catheter and processor components suitable for performingthe methods described herein.

FIGS. 9A and 9B illustrate the principles of triangulation which allowmeasurement of the luminal diameters at various positions along thelength of a body lumen.

FIGS. 10A and 10B illustrate use of a catheter of the present inventionin scanning and obtaining a digital topographic model of an aorticannulus in accordance with the principles of the present invention.

FIG. 11 illustrates an exemplary wire frame model of the type whichmight be provided by the methods of the present invention for use by atreating physician.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIGS. 1A and 1B, a catheter 10 having a shaft 12 with adistal end 14 and proximal end 16 is illustrated and will be described.A distal portion 18 of the shaft 12 is configured to carry anillumination source 20 and a light sensor 22, both which are adapted toaxially translate over the distal portion 18. Typically, theillumination source 20 and light sensor 22 will be coupled so that theywill travel in tandem as illustrated, for example, in broken line inFIG. 1A. The light sensor 22 typically comprises a camera 24 such as acharge coupled device (CCD) sensor, a complementarymetal-oxide-semiconductor (CMOS) sensor, an N-typemetal-oxide-semiconductor (NMOS) sensor, or other solid state cameracomponent, and a lens 26, such as a wide angle or “fish eye” lens, apinhole lens, or the like. The lens 26 and camera 24 are arranged sothat they can detect light which strikes an inside surface of the lumen28 which is disposed around the distal portion 18 of the catheter 10.

The catheter can also optionally have a plurality of electrogram sensingelectrodes 35, 36. The electrodes 35, 36 are particularly useful forpositioning the balloon within the aortic valve annulus and forassessing the region around the aortic valve annulus prior to aorticvalve replacement procedures. The electrodes 35, 36 also allowmonitoring of changes in a patient's electrogram as pressure is appliedto the aortic valve annulus by the balloon. Abnormal changes to theelectrogram could indicate the likelihood of heart block after valvereplacement, if the replacement valve exerts too much pressure on theaortic annulus.

As shown in FIG. 1B, the illumination source 20 will typically project aring of light radially outward, as indicate by broken line 30 so thatthe lens 26 and camera 24 can detect the point 32 where the projectedring of light strikes the inner wall of balloon 28 along acircumferential line 34. As described in more detail below, the angle atwhich the lens and camera detect the location 32 at which the lightstrikes the balloon wall and the distance between the camera and theillumination source can be relied on to measure the radial distanceoutward from the illumination source to the wall of the balloon (andthus the wall of the body lumen) by well-known triangulationcalculations. It will be appreciated, of course, that generally theradial distance will depend on the circumferential location of the pointalong the inner wall of the balloon and the body lumen. Thus, point orlocation 32′ will generally be at a different radial distance than point32 so that the viewing angle from the lens 26 and camera 24 will differ.The same catheter is useful for scanning a closed ended body cavity,such as a left atrial appendage as illustrated in FIG. 1C.

As shown in FIG. 1D, the catheter 10 of FIGS. 1A-1C may be modified tooperate without a balloon. A catheter 110 having a catheter body 112 hasa distal end 114 and a proximal end 116. Instead of a balloon, a distalportion 118 of the catheter body 112 is transparent and configured toreciprocatably carry an illumination source 120 and a light sensor 122in an interior passage or lumen thereof. Typically, the illuminationsource 120 and light sensor 122 are carried by a reciprocatable shaft123 so that they will travel in tandem similarly to the source andsensor in the embodiment of FIGS. 1A-1C. The path of travel, however, isby the interior passage or lumen of the distal portion 118 rather thanby a central shaft, i.e. no central “rail” is needed to guide theillumination source 120 and light sensor 122 although one couldoptionally be provided. The light sensor 122 typically comprises acamera 124 such as a charge coupled device (CCD) sensor, a complementarymetal-oxide-semiconductor (CMOS) sensor, an N-typemetal-oxide-semiconductor (NMOS) sensor, or other solid state cameracomponent, and a lens 126, such as a wide angle or “fish eye” lens, apinhole lens, or the like. The lens 126 and camera 124 are arranged sothat they can detect light which passes through the transparent distalsection 123 of the catheter shaft and strikes an inside surface of thevalve, blood vessel or other luminal surface.

The illumination source 120 will typically project a ring of lightradially outward, as indicate by broken line 130 so that the lens 126and camera 124 can detect the point 132 where the projected ring oflight strikes the inner luminal wall of along a circumferential line 34.As described in more detail below, the angle at which the lens andcamera detect the location 132 at which the light strikes the balloonwall and the distance between the camera and the illumination source canbe relied on to measure the radial distance outward from theillumination source to the wall of the balloon (and thus the wall of thebody lumen) by well-known triangulation calculations. As the camera 124and lens 126 axially scan the luminal wall, the topography of a desiredaxial length of the lumen can be obtained as described above for theembodiments of FIGS. 1A-1C.

When operating without a balloon, blood plasma or another clear fluid(such as saline or a carbon dioxide) may be injected into the visualfield surrounding the distal portion 118 of the catheter to clear thevisual field. The need to clear the visual field will depend on the bodyfluids expected to be surrounding the catheter and the wavelength of theillumination source. For the mouth, esophagus, sinuses, and the like,clearing the visual field may be unnecessary. For the stomach, a gassuch as carbon dioxide may be sufficient. In blood vessels and valves,blood plasma, saline, or the like could be used, although near infraredlight (750 nm to 1400 nm) could be used to penetrate through blood withless absorption than at visible wavelengths. Near infrared wavelengthscould be especially useful when examining relatively small blood vessels(as described below with reference to FIGS. 7A-7C) as the distance thelight would need to travel through blood would be short.

Referring now to FIG. 2, a catheter 200 comprising a catheter shaft 212having a distal end 214 and a proximal end 216 will be described. Alight sensor 222 comprising a camera 224 and lens 226 is fixedly securedat one end of a distal portion 218 attached to the catheter shaft 212.An illumination source 220 is mounted on the distal portion 218 at alocation distal to the light sensor 222. In this embodiment, the lightsensor 222 will also be fixed on the distal portion 218, and theillumination source 220 will be configured so that it can project lightdistally forward (and optionally proximally backward) from the locationat which it is attached. Thus, the illumination source 220 may projectrings, points, lines, or other light patterns at different locationsalong the inner surface of balloon 228. The radial distance of any suchring, line, or point may then be calculated based on the angle at whichthe light beam pattern is projected and the angle at which it isdetected by the light sensor 222. As the distance between theillumination source 220 and the light sensor 222 is fixed, the radialdistance of the point at which the light is striking the balloon may becalculated by conventional triangulation.

FIG. 2A is similar to FIG. 2 but further illustrates a stent S having aplurality of struts 250 lying against the luminal wall LW. The imagingsystem of catheter 200 will be able to clearly delineate the location ofthe stent struts on the luminal wall. Other embodiments of the cathetersof the present invention will also be capable of imaging stents andother previously or concurrently placed luminal implants.

Referring now to FIG. 3, a catheter 300 represents a third embodiment ofthe present invention. The catheter 300 includes a catheter shaft 312having a distal end 314 and proximal end 316. A distal portion 318 ofthe catheter is attached to the catheter shaft 312 and extends distallytherefrom. A single illumination source 320 is adapted to axiallytranslate along an axis of the distal portion 318 and is shown in fullline at travel midpoint of and in broken line at proximal and distaltravel positions.

A proximal light sensor 322 p includes both a camera 324 p and a lens326 p, and a distal light sensor 322 d also includes both a camera 324 dand a lens 326 d. The illumination source 320 will typically project aring-shaped light pattern normal to the axis of travel which willilluminate a generally ring pattern 332 on the inner surface of theballoon 328. At many locations, the point of illumination may bedetectable from both the proximal light sensor 322 p and the distallight sensor 322 d. An advantage of having two light sensors, however,is that in certain locations the point of illumination will bedetectable only by one of the light sensors. For example, theillumination point 332 a may be clearly observed by the proximal lightsensor 322 p, but would be blocked by the anatomy from the distal lightsensor 322 d. Similarly, the illumination point 332 b may be clearlyobserved by the distal light sensor 322 d but would be blocked by theanatomy from being observed by the proximal light sensor 322 p. Theillumination sources 420 a-420 f may also be of different wavelengths orproject distinct patterns if illuminated simultaneously.

Referring now to FIG. 4, a catheter 400 represents a fourth embodimentof a catheter constructed in accordance with the principles of thepresent invention. Catheter 400 includes shaft 412 having a distal end414 and a proximal end 416. A distal portion 418 of the catheter carriesa plurality of fixed illumination sources 420 a-420 f distributed alongits length. The illumination sources 420 a-420 f are located between adistal light sensor 422 d and a proximal light sensor 422 p and within aballoon 428. The light sensor 422 d comprises a camera 424 d and a lens426 d, and the light sensor 422 p comprises a camera 424 p and a lens426 p. Each of the illumination sources 420 a-420 f will usually beconfigured to project a ring-like light pattern 432, as illustrated forillumination source 420 d. The illumination sources may all beilluminated simultaneously but will often be illuminated sequentially,allowing for the light sensors for 422 d and 422 p to triangulate thelocations of the illumination points 432 sequentially as they becomeilluminated. The illumination sources 420 a-420 f may also be ofdifferent wavelengths and/or project distinct patterns if illuminatedsimultaneously.

Referring now to FIGS. 5A and 5B, a catheter 500 having a catheter shaft512 with a distal end 514 and a proximal 516 is illustrated. Thecatheter 500 includes a single light sensor 522 attached at or near thedistal end of the catheter shaft 512. As with previous embodiments, thelight sensor 522 includes a camera 524 and a lens 526. Alight-transmissive element 518 is attached to the distal end of thecatheter shaft 512 and extends distally from the light sensor 522. Thelight transmissive element 518 will typically be formed from an opticalwave guide material suitable for transmitting light from an illuminationsource 520 in a distal direction axially down the element of 518. Aplurality of angled, partially reflective mirrors 550 are placed withinthe light-transmissive element 518 in order to perpendicularly (relativeto a central axis of the catheter shaft 512) reflect a plurality lightrings or other patterns along the luminal wall LW of the body lumen BL.Unlike previous embodiments, the catheter 500 does not include a balloonsurrounding the illumination source 518. Thus, as some of theilluminated rings may not be visible from the light sensor 522, it willbe relatively easy to reposition the catheter in the body lumen.Alternatively, the catheter 500 could be provided with an additionallight sensor at the distal end (not illustrated) in order to allow morecomplete scanning of the interior of the blood vessel to detect theprojected light patterns.

Referring now to FIGS. 6A and 6B, a catheter 600 representing yet afurther embodiment of a catheter constructed in accordance with theprinciples of the present invention will be described. The catheter 600includes a catheter shaft 612 having a distal end 614, a proximal end616, and a distal portion 618. A pair of illumination sources 620 a and620 b are configured to axially translate over an outer surface of thedistal portion 618 of the catheter 600. Each of the illumination ofsources 620 a and 620 b will be associated with at least one lightsensor 622 a and 622 b, as illustrated. The illumination sources 620 aand 620 b will each typically project a partial light ring pattern,typically being somewhat more than a half ring pattern (i.e. extendingover more than 180°), on the luminal wall so that the two partial ringpatterns will overlap to circumscribe substantially the entire crosssection of the lumen, and the light sensors 622 a and 622 b will be ableto detect the light reflected when the partial light ring patternsstrike the inner surface of balloon 628. Usually, one light sensor 622is associated with each illumination source 620, but it will beappreciated that a second distally located light sensor could also beprovided for each of the illumination sources. A particular advantage ofthe configuration of catheter 600 is that perfusion port 652 may beprovided in the catheter shaft 612 in order to allow blood perfusionthru a perfusion lumen 654 and out through a perfusion port 656.

Referring now to FIGS. 7A-7C, a catheter 700 which represents yet afurther embodiment of the present invention is shown to include a shaft712 having a distal end 714 and a proximal end 716. An illuminationsource 720 and a light sensor 722 are fixedly mounted at the distal endof the catheter shaft 712 within an inflatable balloon 728. Neither theillumination source 720 nor the light sensor 722 are configured totranslate on the catheter, and they are located relatively close to eachother along the shaft 712 for a compact configuration. The catheter 700will typically be deployed within the body lumen, usually a bloodvessel, over a guide wire, so that the entire catheter 700 may be drawnor advanced through the body lumen BL in order to scan the luminal wallLW. The illumination source 720 will most typically project a ringpattern allowing the camera 724 and lens 726 of the light sensor 722 tomeasure the luminal dimensions as the catheter is being drawn throughthe lumen, as shown in FIG. 7C. It will be necessary, of course, for thesystem to track the axial location of the illumination source 720 and alight sensor 722 as they are translated through the body lumen. Thesystem can optionally also be configured to track the position of theillumination source in embodiments where the balloon is stationary andthe sensor and/or illumination source is moved inside the balloon. Forexample, the guidewire could be scaled with position markings or otherdetectable indicia (e.g. spaced-apart magnetic regions) that are read ordetected by a sensor on the catheter as the catheter is drawn throughthe body lumen, Alternatively, Hall effect sensors could be employed orthe imaging system could be configured to detect the rate of travel toallow tracking of the device position without additional hardware.

Referring now to FIG. 8, any one of the catheters described previouslymay be employed in a system 800 which includes components whichcommunicate with the catheter to gather data and provide calculations ofthe luminal dimensions. The system components will typically includeboth hardware components and software components. For example, thecatheter will typically require an inflation and deflation system forinflating and deflating the balloon which surrounds the illumination andlight sensing components. Hardware components will typically be neededin order to provide power for illumination and for advancing andretracting the illumination sources and/or light sensors on the catheterand determining their relative positions. Interfaces will also be neededin order to collect the analog and/or digital signals being generated bythe light sensors, cameras, and the like. All of these hardwarecomponents will typically be linked to a computer or other processor,and the computer will typically include an interface, such as a touchscreen, a keyboard, a mouse, voice activation, or the like, and amonitor or display.

Referring now to FIGS. 9A and 9B, an exemplary calculation of a luminalradius R will be described. Using the catheter 10 of FIG. 1 as anexample, the illumination source 20 projects a ring-like pattern overthe inner wall of 29 of the balloon 28. The ring of light willilluminate a circumferential illumination line 60 which circumscribes across-section of the inner surface 29 of the balloon. Thecircumferential illumination line 60 will be detected by the lightsensor 22 where the lens 26 focuses the incoming light on camera 24which typically comprises a CCD, CMOS, or other conventional lightsensor. Information from the camera is fed to a processor or othercalculating system which can determine the incident angle θ. Thedistance D between the illumination source 20 and the light sensor 422is known. Thus, the radius R at any scanned point on the luminal surfacemay be calculated by the simple formula:

R=D tan Θ

It will be appreciated that the radius R at all circumferentiallocations around the interior of the luminal wall LW may be determined,as shown in FIG. 9B, and that the measurements taken in FIG. 9B may berepeated incrementally at different axial locations with the body lumen.Thus, at the end of the procedure, a data matrix including the radiallocations (in three dimensional space) of the illuminated points may becollected. This data matrix will be representative of the shape of thewall of the body lumen in the region that has been scanned.

As shown in FIGS. 10A and 10B, the catheter 10 is placed in an aorticvalve annulus VA and the body wall is scanned circumferentially at anumber of axial locations. While scanning at five locations isillustrated, it will be appreciated that scanning will typically beperformed at a much greater number of axial locations, typically atleast 10, frequently at least 25, and often 100 or more. Scanning ateach axial location results in multiple radial location points, as shownin FIG. 10B. As these data files are built up, it will be possible togenerate not only precise quantitative dimensional information relatingto the anatomical structure being scanned, but it will also be possibleto produce highly accurate three dimensional images of the scannedluminal wall. For example, as shown in FIG. 11, a wire frame model 60may be generated and displayed on the monitor or display screen. Thisimage will be useful for many purposes including assisting in theselection of a prosthesis to be implanted. For example, digital,dimensionally correct models of the prosthesis may be displayedsimultaneously on the monitor or display. The user may then manipulatethe images to determine whether or not the prosthetic image iscompatible with the dimensions of the luminal image. Moreover, asdiscussed above, by inflating a balloon to a pressure which correspondsto the expected outlook force generated by the prosthesis to beimplanted, the dimensions of the fully expanded prosthesis can becompared with the expected deformed dimensions of the body lumen, makingthe comparison even more accurate.

While preferred embodiments of the present invention have been shown anddescribed herein, it will be obvious to those skilled in the art thatsuch embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will now occur to those skilledin the art without departing from the invention. It should be understoodthat various alternatives to the embodiments of the invention describedherein may be employed in practicing the invention. It is intended thatthe following claims define the scope of the invention and that methodsand structures within the scope of these claims and their equivalents becovered thereby.

What is claimed is:
 1. A catheter for scanning a luminal surface of abody lumen to generate electronic signals useful for generating adigital topographic model of the luminal surface, said cathetercomprising: a catheter shaft having a distal end and a proximal end; atleast one illumination source mounted on a distal portion of thecatheter shaft, wherein the illumination source is configured to projectan optical pattern on the luminal wall when the distal portion is in thebody lumen; and at least one sensor mounted on the distal portion of thecatheter and spaced-apart from the illumination source, wherein saidsensor is configured to sense light from the illumination source whichhas been reflected from the luminal wall and to produce an electronicsignal representative of a reflected light pattern; whereby the digitaltopographic model can be generated by triangulation based on theprojected optical pattern, a distance between the illumination sourceand the sensor, and the electronic signal.
 2. A catheter as in claim 1,wherein the at least one illumination source is mounted to axiallytranslate over the distal portion of the catheter shaft.
 3. A catheteras in claim 2, where the at least one illumination source translatesover a distance in the range from 5 mm to 250 mm.
 4. A catheter as inclaim 2, wherein the at least one illumination source projects a ringpattern.
 5. A catheter as in claim 2, wherein the at least one lightsensor is coupled to the at least one illumination source so that thelight sensor translates in tandem with the illumination source.
 6. Acatheter as in claim 2, wherein the at least one light sensor is fixedlymounted on the distal portion of the shaft on one side of the at leastone illumination source.
 7. A catheter as in claim 6, wherein at least asecond light sensor is fixedly mounted on another side of the at leastone illumination source.
 8. A catheter as in claim 7, wherein aplurality of illumination sources is distributed over the distal portionof the shaft.
 9. A catheter as in claim 8, wherein the plurality ofillumination sources is distributed over a distance in a range from 5 mmto 250 mm.
 10. A catheter as in claim 8, wherein at least some of theplurality of illumination sources projects a ring pattern whichcircumscribes a cross-section of the lumen surrounding the source.
 11. Acatheter as in claim 8, wherein at least some of the plurality ofillumination sources project a pattern geometrically different from apattern projected by one or more of the other illumination sources. 12.A catheter as in claim 8, wherein at least some of the plurality ofillumination sources project a pattern having a different lightwavelength than projected by one or more other illumination sources. 13.A catheter as in claim 1, further comprising a balloon which isinflatable over the distal portion of the catheter shaft to isolate aregion over the at least one illumination source and the at least onesensor.
 14. A catheter as in claim 13, wherein the balloon is elastic.15. A catheter as in claim 13, wherein the balloon is inelastic.
 16. Acatheter as in claim 13, wherein the balloon has a reflective interiorsurface.
 17. A catheter as in claim 11, wherein the illumination sourceand the light detector are both disposed within the balloon and theballoon is configured to be drawn through the body lumen to collect datafrom the reflected light.
 18. A catheter as in claim 1, wherein thecatheter shaft comprises a catheter body and at least a distal portionof the catheter body is transparent, wherein the illumination source andcamera are disposed within said transparent distal portion of thecatheter body.
 19. A catheter as in claim 18, wherein the illuminationsource and camera are reciprocatably disposed within said transparentdistal portion of the catheter body.
 20. A system comprising: a catheteras in claim 1; and a processor connected to receive the electronicsignal and configured to generate the digital topographic model bytriangulation based on the projected optical pattern and the distancebetween the illumination source and the sensor.